为表格实现斑马线效果

function stripeTables() {
    if(!document.getElementsByTagName) return false;
    var tables = document.getElementsByTagName("table");
    var odd,rows;
    for(var i=0;i<tables.length;i++){
        odd = false;
        rows = tables[i].getElementsByTagName("tr");
        for(var j=0;j<rows.length;j++){
            if(odd == true){
                rows[j].style.backgroundColor = "#ffc";
                //addClass(rows[j],"odd");编写好了addClass()函数，就可直接引用
                odd = false;
            } else {
                odd =true;
            }
        }
    }
}